1. Field of the Invention
The present invention relates to a motor-driven power steering apparatus.
2. Description of the Related Art
In a motor-driven power steering apparatus, as shown in Japanese Patent Application Laid-Open (JP-A) No. 11-118631 (patent document 1) and JP-A No. 2008-37189 (patent document 2), there is a structure in which an input shaft and an output shaft are coaxially coupled via a torsion bar. A drive gear to which an electric motor is coupled is pivoted to a gear housing. A driven gear engaging with the drive gear is fixed to an intermediate portion of the output shaft. A torque detecting structure detecting a steering torque applied to the input shaft is provided between the input shaft and the output shaft. A spirally wounded spiral cable is provided around the same axis of the input shaft and the output shaft in an inner portion of the gear housing. One end portion of the spiral cable is connected to the torque detecting structure, another end portion of the spiral cable is connected to a detection result pickup portion. Driving of the electric motor is controlled on the basis of a steering torque which the torque detecting structure detects.
In a manufacturing process of the motor-driven power steering apparatuses which are described in JP-A Nos. 11-118631 and 2008-37189, there is a handling stage such as a stage of conveying an intermediate assembly which is assembled with the input shaft, the output shaft, the torsion bar, the drive gear, the driven gear, the torque detecting structure and the spiral cable into the gear housing, but the electric motor has not been assembled yet, and the like.
In the handling stage of the intermediate assembly mentioned above, conventionally the rotation of the input shaft, the output shaft and the gear shaft of the drive gear which are exposed from the gear housing is not regulated, and these shafts can be easily rotated by an external rotating force. When these shafts are freely rotated, the spiral cable in an inner portion of the gear housing is freely wound around. In accordance with this, a number of winding is increased or decreased in comparison with a state in which a winding state of the spiral cable is neutral. In the case that the number of winding of the spiral cable is abnormally increased, a disconnection of the spiral cable or the like is caused, and there is a risk that the torque can not be detected. In the case that the number of winding is decreased, the spiral cable is stuck fast to the spiral cable cover, and an increase of the steering torque may be caused.